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Electrical > Automation - weeks 5/6 > Flashcards

Automation - weeks 5/6 Flashcards

1
Q

define: digital

A
  • device has only two states (eg. magnetic relays)
    –> ON
    –> OFF
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2
Q

define: “digital logic”

A
  • circuits using gates (solid-state control devices)
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3
Q

what are 5 basic types of gates

A
  • AND
  • OR
  • NOR
  • NAND
  • INVERTER
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4
Q

what are 5 different types of logic

A
  • RTL: resistor-transistor logic
  • DTL: diode-transistor logic
  • TTL: transistor-transistor logic
  • HTL: high-transit logic
  • CMOS: comes from COSMOS complementary, symmetry metal-oxide-semiconductor
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5
Q

the AND gate may have ____ inputs, and ____ output

A
  • may have several inputs
  • only one output
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6
Q

the AND gate must have all of its inputs _______ in order to get an output

A
  • all of its inputs high
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7
Q

the OR gate has ____ output when either or both of inputs are ____

A
  • has high output when either or both of inputs are high
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8
Q

the EXCLUSIVE OR gate has ____ output when _____ of its inputs are high

A
  • high output when either, but not both, of its inputs are high
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9
Q

the INVERTER has ____ input(s) and _____ output(s)

A
  • one input
  • one output
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10
Q

with the INVERTER, the output is…

A
  • inverted
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11
Q

describe computer logic w the INVERTER

A
  • circle drawn on gate means invert
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12
Q

describe NEMA logic with the INVERTER

A
  • X used to show gate is inverted
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13
Q

what symbol is used for NOR gate

A
  • same symbol for OR gate with an inverted output
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14
Q

the NOR gate can be made by…

A
  • connecting an INVERTER to output of an OR gate
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15
Q

with the NOR gate, the output is _____ when any input is high

A
  • output is zero (or low) when any input is high
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16
Q

the NAND gate means…

A
  • “NOT AND” gate
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17
Q

what symbols are used for the NAND gate

A
  • same symbols as AND gate w inverted outputs
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18
Q

any input of a NAND gate is _____; output is _____

A
  • input is low
  • output is high
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19
Q

describe the basic gate with the NAND gate

A
  • can be used to make any other gates
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20
Q

digital logic gates are generally houses in _____ pin, ____ packages

A
  • 14 pin, IC packages
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21
Q

what logic is frequently used in digital logic gates

A
  • TTL logic, 7400 family
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22
Q

with integrated circuits, what type of diagram is used when connecting or testing integrated circuits

A
  • use a connecting diagram
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23
Q

integrated circuits must be tested by _________, then testing ________

A
  • must be tested by connecting power
  • then testing inputs and outputs w special test equipment
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24
Q

with integrated circuits, who determines which section of the circuit is not operating and replaces that module?

A
  • electrician
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25
Q

why is a magnetic relay considered a digital device

A
  • bc it only has 2 states: on or off
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26
Q

what are the 5 basic logic gates

A
  • AND
  • OR
  • NOR
  • NAND
  • INVERTER
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27
Q

transistor-transistor logic operates on…

A
  • 5 volts
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28
Q
  • high transit logic operates on…
A

15 volts

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29
Q

most gate circuits are multi-input, ____ output devices

A

single

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30
Q

how many input & outputs does the inverter gate have

A
  • 1 input, 1 output
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31
Q

when using TTL logic, 5 volts would indicate a high or low lvl

A

high

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32
Q

when using TTL logic, 0 volts would indicate a high or low lvl

A

low

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33
Q

when an inverter gate is used, is the input or output inverted

A

output

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34
Q

with an AND gate, if all inputs are high, the outputs are ____

A

high

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35
Q

with an OR gate, if one input is high, the output is ____

A

high

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36
Q

with a NOR gate, if one is high, the output is ____

A

low

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37
Q

with a NAND gate, if all inputs are high, the output is _____

A

low

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38
Q

a logic gate in which the output is always opposite the input is the…

A
  • inverter
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39
Q

what symbol is used to represent “invert” when NEMA logic symbols are used?

A

X

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40
Q

what symbol is used to represent “invert” when computer logic symbols are used?

A

O

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41
Q

if an INVERTER is connected to the output of an NAND gate, what logic gate is formed

A

AND

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42
Q

if an INVERTER is connected to the output of an OR gate, what logic is formed

A

NOR

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43
Q

when using a two-input AND gate, what conditions of input must be met to have an output

A
  • both inputs must be high
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44
Q

when using a two-input OR gate, what conditions of input must be met to have an output

A
  • either input may be high
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45
Q

when using a two-input NAND gate, what conditions of input must be met to have an output

A
  • either input may be low
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46
Q

when using a two-input NOR gate, what conditions of input must be met to have an output

A
  • both inputs must be low
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47
Q

explain the difference between an OR gate and an EXCLUSIVE OR gate

A
  • OR gate has high output when either or both inputs are high, exclusive has high output when either but not both inputs are high
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48
Q

integrated circuits can be tested with a:
a. volt meter
b. watt meter
c. ammeter

A

none of the above

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49
Q

the gate that is often referred to as the basic gate is…

A

NAND gate

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50
Q

digital circuit will be designed to perform same function as a ________ circuit

A
  • common relay
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51
Q

a relay circuit is a ________ circuit with ______ protection

A
  • a basic stop-start, push-button circuit w overload protection
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52
Q

with a start-stop push-button control, if the motor is overloaded what happens?

A
  • too much current will flow thru circuit
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53
Q

with a start-stop push-button control, if current greater than normal flows through overload heater, what happens?

A
  • the heater produces more heat than normal
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54
Q

with a start-stop push-button control, when the motor is overloaded, if current becomes high enough, it will cause what to happen?

A
  • normally closed overload contact to open
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55
Q

with a start-stop push-button control, the overload contact is electrically isolated from??

A
  • heater –> can be connected to different voltage source than motor
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56
Q

with a start-stop push-button control, what happens is the overload contact opens

A
  • control circuit is broken
  • relay de-energizes as if STOP button had been pushed
  • after overload contact has been reset to normally closed position, coil will remain de-energized until START button is pressed again
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57
Q

see slides 10,11,12,13 –> dont know how to make cards on this bc i dont understand lol

A

…

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58
Q

with a start-stop push-button control, what happens when START button is pushed (6)

A
  • a high is connected to input A or OR gate –> causes output of OR gate to change to high
  • high output connected to input A of AND gate
  • AND gate now has both of its inputs high
  • input B of the OR gate becomes high also
  • OR gate has a high connected to B input –> output will remain high when push button is returned to open condition and input A becomes low
  • next, connect overload contact to circuit –> will cause output of circuit to turn off if it opens
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59
Q

slide 16 –> idk what they mean by previois circuit??

what are problems with previous circuit (3)

A
  • if overload contact is reset, output will immediately change back to a high state
  • if overload contact opens and is then reset in relay circuit, relay will not restart itself
  • START button must be pushed to restart circuit (could become a safet6y hazard)
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60
Q

slide 18, also dont understand what they are referring to

other problems to be corrected

A
  • gate could still assume either condition –> always connect inputs to definite high or low
  • if resistor pulls an input low, gate will have a voltage drop at output –> push button can produce a high at input by adding an INVERTER
  • circuit was used to control a 120 volt AC motor –> connect a solid state relay to output in place of LED
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61
Q

describe the purpose of analog sensing

A
  • continuously varying
  • designed to sense:
  • voltage
  • current
  • speed
  • pressure
  • temp
  • humidity
    etc.
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62
Q

with analog sensing, a special module mounts on…

A
  • I/O rack of PLC
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63
Q

with analog sensing, the analog sensory operates between…

A
  • a range of settings
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64
Q

analog sensing is used to indicate…

A
  • a range of values instead of operating in an on/off mode
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65
Q

pressure sensors can be constructed in several ways. describe the common method

A
  • let pressure sensory operate current generator producing currents between 4 and 20 milliamperes
  • sensory should produce a certain amt of current to eliminate voltage drop on lines
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66
Q

most analog sensors produce ______ signals. how much exactly?

A
  • very weak
  • 0 to 10 volts or 4 to 20 milliamperes
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67
Q

describe the installation of analog sensors in enviros w intense magnetic fields and large voltage spikes (2)

A
  • easy to lose input signals in electrical noise
  • special precautions should be taken when installing signal wiring between sensor and input module
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68
Q

describe installation of analog sensors (3)

A
  • keep wire runs short
  • plan signal cable route
  • use shielded cable
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69
Q

describe grounding of analog sensors (2)

A
  • not uncommon for different pieces of equipment to have ground lvls several volts apart
  • large cable is sometimes used to tie two pieces of equipment together, forces them to exist at same potential
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70
Q

when grounding analog sensors, _______ method is not practical

A
  • brute-force –> shield of signal cable is grounded at one end
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71
Q

what is the preferred method of grounding analog sensors

A
  • to ground shield at the sensory
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72
Q

the differential amplifier is used to… (3)

A
  • help overcome problem of induced noise
  • detects voltage difference between pair of signal wires
  • amplifies this difference
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73
Q

with differential amplifiers, since induced noise level should be same in both conductors, amplifier will _______ the noise

A
  • ignore
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74
Q

if an analog sensor producing 50 millivolt signal, signal is applied to _______ but induced noise is at a lvl of ______ volts

A
  • signal is applied to input module, but induced noise is at a lvl of 5 volts
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75
Q

with a differential amplifier, noise lvl is ____ times greater than signal lvl

A
  • 100 times greater
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76
Q

with differential amplifier, induced noise lvl is _______ for both of input conductors

A

same

77
Q

differential amplifier ignores ___ volt noise and amplifies only _____________

A
  • ignores 5 volt noise
  • amplified only voltage difference, 50 millivolts
78
Q

what does analog mean

A
  • continuously varying
79
Q

what are analog inputs used to sense (6)

A
  • voltage
  • current
  • speed
  • pressure
  • temp
  • humidity
80
Q

analog sensors are constructed to produce 2 types of output signals. what are the 2 types of signals, which is preferred and why?

A
  • voltage and current
  • current is preferred bc it eliminates the problem of voltage drop
81
Q

would pushbuttons, float switches, and limit switches be considered analog devices

A

no

82
Q

signal wires from a sensor to a controller should be run as _______ as possible so that the conductors are not exposed to surrounding magnetic fields

A
  • short
83
Q

when installing signal wires for analog sensors, what type of wire/cable should be used

A

shielded cable

84
Q

what angle should signal wires cross power wires

A

90*

85
Q

shielded cables are used to help prevent induced voltages caused by surrounding

A
  • magnetic field
86
Q

when deciding whether to use a 1-5 volt output sensor or a 4-20 mA output sensory what would be a major factor in the decision

A
  • distance from the sensory to the controller
87
Q

a controller is used to operate a modulating valve. if the controller has a 4-20 mA output and the valve is open 67%, the controller’s mA output would be _____ mA

A

14.72 mA

88
Q

a controller is used to operate a modulating valve. if the controller has a 1-5 volt output and the valve is open 67%, the controllers voltage output would be ___ volts

A

3.68 volts

89
Q

the flow rate in a pipe needs to be monitored. a flow sensor with a 4-20 mA output is used as an input to a PLC. if the PLC was receiving a 9.45 mA current, what would the percentage of flow be

A

34%

90
Q

the pressure in a chamber needs to be monitored. the pressure range is 0 to 90 PSI. a pressure sensory with a 1-10 voltage output as an input to a PLC. if the PLC was receiving 6.85 volts, what would the pressure in the chamber be?

A

58.5 PSI

91
Q

when installing shielded cables for analog sensors, should the shield be grounded at both ends

A
  • one end
92
Q

what is the preferred location to ground the shield

A
  • at the sensor
93
Q

the first PLC was invented by… for use in the _____ industry

A

richard morley in 1969 for use in the auto industry

94
Q

PLC processors still process info in which way?

A
  • internally via gate logic (AND, OR, NAND, etc.) but they have been modified such that the PLC programs may be entered using conventional ladder logic
95
Q

PLCs are very similar to which diagrams, making it user friendly

A
  • similar to Line Diagrams
96
Q

what are 5 basic parts of a PLC

A
  • power supply
  • CPU
  • I/O section
  • rack
  • loader
97
Q

what is the purpose of power supply

A
  • supplies power for the CPU and the I/O logic
98
Q

what is the purpose of the CPU

A
  • acts as a computer
99
Q

what is the purpose of the I/O section

A
  • real world devices are wired to the modules
  • inputs: push buttons, limit switches, etc.
  • outputs: starter coils, solenoids, etc.
100
Q

what is the purpose of the rack

A
  • houses the power supply, CPU, and I/O sections
101
Q

what is the purpose of the loader

A
  • can be a laptop computer or a hand held computer
102
Q

what are advantages of a PLC over conventional control (7)

A
  • more internal relays & associated contacts to replace CR’s, TR’s, and counters
  • flexibility of quick & easy changes, w little or no reqiring of I/O
  • internal relays & contacts have no moving parts
  • less cost & space required for initial installation and/or future modifications
  • less cost due to reduced hardware, hard wiring, and associated down time requirements
  • less device maintenance compared to other devices
  • easy expansion of I/O capability
103
Q

the National Eelectrical Manufacturing Association standards for programmable controllers recommend that consideration be given to:

A
  • the use of emergency stop functions that are independent of the programmable controller

“when the operator is exposed to machinery, such as loading or unloading a machine tool, or where the machine cycles automatically, consideration should be given to the use of an electromechanical override or other redundant means, independent of the controller, for starting or interrupting the cycle”

104
Q

the field wiring from electrical devices are terminated at the ________. they are designated to be either an _______ or _____ module

A

I/O modules
- input module
- output module

105
Q

LED’s visible on the PLS are used to indicate if an input or output is ________

A

on or off (high or low)

106
Q

with I/O modules, the modules employ… what does this help do>

A
  • opto-isolation to isolate the field wiring from the PLC circuitry
  • this helps to eliminate damage caused by spiked and harmonics present on the line circuitry
107
Q

some PLCs contain a ____ power source

A

DC power source

108
Q

a DC power source can be used to…

A
  • feed input devices
  • if inputs are DC, correct polarities must be adhered to
109
Q

module voltages range from…

A

5V DC to 240V AC/DC

110
Q

input devices are categorized in two ways, what are they?

A
  • discrete (digital)
  • analog
111
Q

digital/discrete inputs are recognized as… (2)

A
  • ON or
  • OFF
112
Q

digital/discrete inputs are recognized as… (2)

A
  • ON or
  • OFF
113
Q

if a doscrete device is connected to an input of a module, the module determines and communicates…

A
  • the state of the limit switch to the processor
114
Q

if the switch is open w discrete inputs, the module indicate….

A
  • to the processor that the limit switch is OFF
  • this condition is stored in the processor memory as a zero
115
Q

with discrete inputs, if the swicth closes, the module will indicate to the processor that the limit switch is…

A
  • ON
  • the condition is then stored in the processor memory as a one (1)
116
Q

with discrete inputs, all info stored in the processor memory about the status or condition of a discrete input device is always stored as a ______

A

1 or 0

117
Q

describe how analog inputs work

A
  • send a constant signal to a module
  • the module then communicates the magnitude or strength of the signal to the processor
  • the magnitude of voltage or current masy be used to represent some sort of condition

ex. a certain voltage might represent the speed of a motor (5 volts corresponds to 200 rpm, 10 volts to 400 rpm, etc.)

118
Q

external relays (interposing relays)

*idk how to break this into smaller cards)

A
  • larger solenoids, motor starter coils, and other heavier control loads occasionally draw a fair amt of current
  • external relays are sometimes fed from outputs when currents or voltages are beyond the rating of the module output
  • these interposing relays are used to switch the heavier control device
  • the rating of PLC I/O is typically 5A/250V
119
Q

Random Access Memory (RAM) is used to store __________. describe the ability to erase or change this

A
  • PLC programs
  • can be erased or changed over & over
120
Q

Read-Only Memory (ROM) is used by the manufacturer to….

A
  • store the operating system
121
Q

can data written to a ROM be removed?

A
  • cannot be removed, only read
122
Q

both ROM and RAM styles of memory allow….. this means that RAM should be thought of as _____ RAM and ROM thought of as ____ RAM

A
  • random access
  • RAM = read-write RAM
  • ROM = read-only RAM
123
Q

Electrically Erasable Programmable Read-Only Memory is a special type of meory that can be erased by….

A
  • exposing it to an electrical charge
124
Q

Erasable Programmable Read-Only Memory (EPROM) can be erased by…

A
  • exposing it to ultraviolet light
125
Q

EPROM and EEPROM memory is used to store…

A
  • PLC backup programs
126
Q

integrated circuits (memory chips) used in the processor construction, can be separated into 2 distinct groups

A
  • volatile
  • non-volatile
127
Q

what are volatile integrated circuits? what is an example?

A
  • memory that loses its stored info when power is removed
  • even a momentary loss of power will erase any info stored or programmed on a volatile integrated circuit
    ex. RAM
128
Q

what is non-volatile memory? what are examples

A
  • memory that is able to retain stored info when power is removed accidentally or intentionally
    ex. ROM, EEPROM, EPROM
129
Q

what are backup batteries

A
  • factory installed in various PLCs within either the power supply or the processor
130
Q

backup batteries are used to protect…

A
  • a PLCs volatile memory
131
Q

all PLC batteries should be replaced every __ years

A

5

132
Q

what are the 2 most common devices used to program a PLC

A
  • laptop computers
  • hand held units
133
Q

are laptops or hand-held units more useful in troubleshooting and wide?

A
  • laptops bc the view screen is larger = a large portion of program may be viewed at one time
134
Q

the AND gate functions as …

A
  • 2 switches wired in a series
135
Q

with an AND gate, ____ A and B must be ____ before the output can be hig

A

both, high

136
Q

with OR gates, if ____ A or B is _______, the output will be high

A
  • either, high
137
Q

the OR gate functions as ….

A

2 switches wired in parallel

138
Q

a NAND gate combines…

A
  • a NOT gate with an AND gate
139
Q

with a NAND gate, the output normally achieved from an AND gate is ….

A
  • inverted
140
Q

a NOR gate combines…

A
  • a NOT gate and an OR gate
141
Q

with a NOR gate, the output normally achieved from an OR gate is….

A
  • inverted
142
Q

the NOT gate is often referred to as an…

A
  • inverted
143
Q

a NOT gate has ___ input and ___ output

A
  • 1 and 1
144
Q

with a NOT gate, if the input is ______, then the output will be high

A

low

145
Q

a PLC is normally programmed using….

A
  • ladder logic
146
Q

why is the use of ladder logic for a PLC a “wise choice”

A
  • it closely resembles the way circuits are hard wired as per Line Diagram style schematics
147
Q

what are 5 types of programming contacts

A
  • examine on
  • examine off
  • force
  • force off function
  • force on function
148
Q

with examine on, a N.O contact symbol is actually an ….

A
  • an instruction –> telling the processor to look for an ON or (1) condition at the bit address (in the word) assigned to the N.O instruction
149
Q

with examine on, if an ON condition exists…

A
  • the instruction is said to be logically true
  • this is similar to saying “if the contact closes, current may flow across the contact”
150
Q

with examine off, a N.C contact symbol is an…

A
  • instruction –> it tells the processor to look for an OFF or (0) condition at the bit address (in the word) assigned to the N.C instruction
151
Q

with examine off, if an OFF condition esists, the instruction is said to be ….

A
  • logically true
  • this is similar to the saying “if the contact remains closed, current may flow across the contact”
152
Q

what is force

A
  • a mode of operation or instruction that allows the operator (as opposed to the processor) to control the state of an input or output device
153
Q

what is force off function

A
  • a feature that allows the user to change the state of any input or output by means of the programmer, independent of the PLC program
154
Q

what is force on function

A
  • a feature that allows the user to change the state of any input or output by means of the programmer, independent of the PLC program
155
Q

Note: the force on and force off feature should never be used by personnel who do not completely understand the circuit and the process machinery or driven equipment. an understanding of the potential effect that forcing a given contact or coil has on machine operation is essential if hazardous or destructive operation is to be avoided

A
156
Q

a ladder diagram should be read…

A
  • left to right and from top to bottom
157
Q

in ladder diagrams, the vertical circuitry lines, known as rails, represent…

A
  • the voltage potential of the control circuit
158
Q

with ladder diagrams, the potential may vary anywhere from…

A

6V to 600 V AC or DC

159
Q

with ladder diagrams, standard labeling of the rails that represent an AC source is….. that represent a DC source is…

A

L1 and L2 represent an AC source

+ and - represent a DC source

160
Q

the rails of a ladder diagram may be marked X1 and X2 (N) when the….

A
  • voltage potential is supplied by a grounded transformer
161
Q

with a ladder diagram, the horizontal lines that connect to the rails are generally referred to as…

A
  • rungs
162
Q

with ladder diagrams, it is good practice to show all devices or components in order of….

A
  • importance
163
Q

with ladder diagrams, when is a stop button shown in comparison to a sgtart button

A
  • a stop button is almost always shown before a start button
164
Q

with ladder diagrams, electrical devices or components are shown in their ______ condition

A
  • normal condition
165
Q

what is the normal condition of electrical diagrams

A
  • is the de-energized (OFF) condition with no external forces such as pressure or flow acting on any of the devices
166
Q

before installing the rack or chassis, consideration must be given to the enviro it will be housed in (6)

A
  • temp
  • dust
  • vibration
  • humidity
  • electrical disturbances from electrical equipment and wiring
  • trouble shooting accessibility
167
Q

the ambient temp of the PLC location should never be lower than ____ or higher than ____

A
  • lower than 0*C
  • or higher than 32*C
168
Q

describe the process of convection

A
  • fans may not be supplied w I/O racks, cooling may be accomplished by heat from water components rising and drawing cool air in through the bottom of the rack = result is constant mvmt of air
169
Q

what should be considered for controlling the temp of the enclosure housing the PLC

A
  • consideration should be given to the use of cabinet cooling fans and heaters
170
Q

what happens if dust is permitted to accumulate within processors, power supplies, and I/O modules

A
  • it will prevent effective heat dissipation of electronic components
171
Q

due to unwanted PLC system failures, it is important for enclosures housing PLC racks to be ….. r.t dust

A
  • to be both dust tight & big enough to allow for ample air circulation for heat dissipation
  • installation manuals will usually include minimum size enclosure specifications
172
Q

excessive vibration can lead to…

A
  • early component failure
173
Q

due to the negative effects of excessive vibration, it is important to mount PLC equipment on..

A
  • solid, non-vibrating surfaces
174
Q

vibration effects from equipment must be minimized to assure…

A
  • longevity of the equipment
175
Q

humidity, while normally not a problem, must be considered when installing a PLC. Why?

A
  • exposing electronic equipment to high humidity lvls over an extended period of time can reduce component life and affect the operation
176
Q

while it is commonly useful for PLC’s and programming devices to be installed in central locations such as control centers, the use of remote I/O racks allows…

A
  • inputs and outputs modules to be installed at the same location as the equipment being controlled
177
Q

the risk of a line disturbance occurring ______ as the wire length between the processor and the remote rack increases

A

increases

178
Q

the decimal system uses ___ unique numbers, which are __ thru __

A
  • uses 10 unique digits, 0 thru 9
179
Q

a numbering system that uses 10 digits is said to have a base of ___

A

10

180
Q

the binary system uses __ digits, what are they

A
  • 2 digits, 1 and 0
181
Q

the binary system has a base of ___

A

2

182
Q

like the decimal system, in the binary system each digit has a certain…

A
  • place value
183
Q

describe the place values in the binary system

A
  • the first place to the left of the starting point is the units or 1s location (260)
  • the next place, to the left of the units place, is the 2s place, or base 2^1
  • the next place value is the 4s, or 2^2
  • then 8s, or base 2^3 and so on
184
Q

the octal system is made up of __ digits, which numbers?

A
  • 8 digits, 0 thru 7
185
Q

describe the place values in the octal system

A
  • first digit to the left of the octal point is the units place, or 1s, and has a base or power of 8^0
  • the nexgt place is the 8s or base 8^1
  • the next place is 64s or base 8^2
  • followed by 512s, or base 8^3
  • then 4096s or base 8^4 and so on
186
Q

the hexadecimal system has ___ digits, what numbers are used?

A
  • 16 digits
  • 0 thru 9, then A, B, C, D, E, and F
  • next group is: 10,11,12,13,14,15,16,17,18,19,1A,1B,1C,1D,1E,1F
187
Q

describe the place values in the hexadecimal system

A
  • 1’s-16^0
  • 16’s - 16^1
  • 256’s - 16^2
  • 4096 - 16^3
  • 65536’s - 164 and so on
188
Q

the binary coded decimal system uses the decimal numbers

A

0 thru 9
- the decimal numbers are individually converted to their binary equivalents , the binary numbers can then be deposited into words rather easily

Electrical (13 decks)

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